MESOSCALE PRECIPITATION DISCUSSION 0328
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
321 PM EDT TUE JUN 19 2018

AREAS AFFECTED...SOUTHEAST MT...EASTERN WY...

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 191920Z - 200020Z

SUMMARY...INCREASED MOISTURE AND SATURATED SOILS POSE SCATTERED
LOCALIZED FLASH FLOOD RISKS.

DISCUSSION...GOES-16 WV SUITE DEPICTS A STRONG COMPACT VORTICITY
CENTER TRACKING ACROSS SOUTH CENTRAL WY ATTM WITH BROAD DIFFLUENT
UPPER LEVEL FLOW DOWNSTREAM PROVIDING STRONG UPPER LEVEL SUPPORT
FOR CONVECTION.  WEAK BUT MOIST UPSLOPE FLOW FEEDS THE LOW LEVEL
ENVIRONMENT ENOUGH TO SUPPORT TPWS TICKING UP TO .9 TO 1.1" ALONG
THE FRONT RANGE TO EASTERN SIDE OF THE BIG HORN RANGE.  GOES-1
MINUTE IR/VIS SHOWS THE RAPID DEVELOPMENT OF NUMEROUS CELLS FROM
THE S BIG HORNS TO DENVER...WHILE CONVECTIVE VIGOR DRIVEN BY
INSTABILITY WILL START WITH LARGE HAIL CELLS WILL HAVE MODERATE
RAINFALL WITH IT AS WELL...WHICH WILL BECOME INCREASINGLY MORE
EFFICIENT WITH SATURATING OF THE PROFILE BOTH THROUGH EVAPORATION
BUT ALSO THE INCREASING DEPTH OF THE MOISTURE AS THE CELLS MOVE
FURTHER WEST. 

CELL MOTIONS WILL BE SLOWER WITH INCREASED MST FLUX AND SOME
TRAINING ALONG THE DEFORMATION ZONE NORTH AND EAST OF THE S/W FROM
FREEMONT COUNTY, WY TOWARD THE BLACK HILLS AS IT EJECTS EASTWARD
THIS AFTERNOON INTO EVENING.  ADDITIONALLY...GIVEN THE COMPACT
NATURE OF THE S/W THE TAIL END OF THE DPVA IS LIKELY TO ORIENT
ACROSS NE CO REDUCING EASTWARD PROGRESS (PER BUNKER RIGHT MOVING
SUPERCELL VECTORS AROUND 15-20KTS).  EVEN THOUGH CELL MOTIONS
BETWEEN THESE AREA WILL BE QUICKER...HIGH RAINFALL RATES OVER
1.0"/HR ARE FALLING OVER SATURATED SOILS WHERE AHPS 7DAY PCT OF
NORMAL VALUES ARE 300+% ABOVE AVERAGE AND FFG VALUES ARE REDUCED
TO LESS THAN 1"/HR IN MUCH OF THE CONCERNED AREA.  HI-RES CAMS
SHOW THE SCATTERED NATURE OF 1-2" TOTALS BUT THERE IS A GOOD
CONSENSUS TO SUGGEST LOCALIZED FLASH FLOODING IS POSSIBLE (ESP. IN
SPECIFIC AREAS STATED ABOVE).

GALLINA

ATTN...WFO...BOU...CYS...RIW...UNR...

ATTN...RFC...MBRFC...

LAT...LON   44710403 43960317 43120295 42400312 41890310
            41460277 40950276 40350367 39750513 40840550
            41520605 41960672 42400691 42740733 43370755
            43890714 44150651 44590520